Multiangle Sonar Imaging for 3-D Reconstruction of Underwater Objects in Shadowless Environments

In the realm of underwater detection technologies, reconstructing the three-dimensional structure of underwater objects is crucial for applications such as underwater target tracking, target locking, and navigational guidance. As a primary tool for underwater detection, acoustical imaging faces significant challenges in recovering the three-dimensional structure of objects from two-dimensional images. Current 3-D reconstruction methods mainly focus on reconstructing objects at the riverbed, overlooking the reconstruction of objects in the water in the absence of shadows. This study introduces a multiangle shape and height recovery method for such specific situations. By fixing the sonar detection angle and utilizing ViewPoint software to measure the contours of objects at different depths, a superimposition technique for two-dimensional sonar images was developed to achieve three-dimensional reconstruction of shadowless sonar image data. The proposed method is specifically designed for scenarios with diffuse echoes, where the sound waves scatter from rough surfaces rather than reflect specularly from smooth surfaces. This limitation ensures the method's applicability to objects lacking strong mirror-like reflections. This technique has been validated on three different categories of targets, with the reconstructed 3-D models accurately compared to the actual size and shape of the targets, demonstrating the method's effectiveness and providing a theoretical and methodological foundation for the 3-D reconstruction of underwater sonar targets.